package com.example.shoppinglist;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ObjectAnimator;
import android.animation.TypeEvaluator;
import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.support.v4.widget.DrawerLayout;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewTreeObserver;
import android.widget.AbsListView;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map.Entry;

import com.example.shoppinglist.ShoppingListActivity.DrawerListAdapter;

public class DrawerDynamicListView extends ListView {

	private final int SMOOTH_SCROLL_AMOUNT_AT_EDGE = 15;
	private final int MOVE_DURATION = 150;
	private final int LINE_THICKNESS = 15;

	public LinkedHashMap<Integer, ShoppingList> mLists;

	private int mLastEventY = -1;

	private int mDownY = -1;
	private int mDownX = -1;

	private int mTotalOffset = 0;

	private boolean mCellIsMobile = false;
	private boolean mIsMobileScrolling = false;
	private int mSmoothScrollAmountAtEdge = 0;

	private final int INVALID_ID = -1;
	private long mAboveItemId = INVALID_ID;
	private long mMobileItemId = INVALID_ID;
	private long mBelowItemId = INVALID_ID;

	private BitmapDrawable mHoverCell;
	private Rect mHoverCellCurrentBounds;
	private Rect mHoverCellOriginalBounds;

	private final int INVALID_POINTER_ID = -1;
	private int mActivePointerId = INVALID_POINTER_ID;

	private boolean mIsWaitingForScrollFinish = false;
	private int mScrollState = OnScrollListener.SCROLL_STATE_IDLE;

	private DrawerLayout mDrawerLayout;

	public DrawerDynamicListView(Context context) {
		super(context);
		init(context);
	}

	public DrawerDynamicListView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		init(context);
	}

	public DrawerDynamicListView(Context context, AttributeSet attrs) {
		super(context, attrs);
		init(context);
	}

	public void init(Context context) {
		setOnItemLongClickListener(mOnItemLongClickListener);
		//setOnItemClickListener(mOnItemClickListener);
		setOnScrollListener(mScrollListener);
		DisplayMetrics metrics = context.getResources().getDisplayMetrics();
		mSmoothScrollAmountAtEdge = (int)(SMOOTH_SCROLL_AMOUNT_AT_EDGE / metrics.density);
	}

	//listens for long clicks on any items in the listview. When a cell has
	// been selected, the hover cell is created and set up
	private AdapterView.OnItemLongClickListener mOnItemLongClickListener = new AdapterView.OnItemLongClickListener() {
		public boolean onItemLongClick(AdapterView<?> arg0, View arg1, int pos, long id) {
			mTotalOffset = 0;

			int position = pointToPosition(mDownX, mDownY);
			int itemNum = position - getFirstVisiblePosition();

			View selectedView = getChildAt(itemNum);
			mMobileItemId = getAdapter().getItemId(position);
			mHoverCell = getAndAddHoverView(selectedView);
			selectedView.setVisibility(INVISIBLE);
			//int checkedItemPosition = getCheckedItemPosition();
			//setItemChecked(checkedItemPosition, false);
			mCellIsMobile = true;
			mDrawerLayout.requestDisallowInterceptTouchEvent(true);
			updateNeighborViewsForID(mMobileItemId);

			return true;
		}
	};

//	private AdapterView.OnItemClickListener mOnItemClickListener = new AdapterView.OnItemClickListener() {
//		public void onItemClick(AdapterView<?> arg0, View arg1, int pos, long id) {
//			long itemId = ((ShoppingItem) getAdapter().getItem(pos)).getId();
//			fragment.editItem(itemId);
//		}
//	};

	//creates the hover cell with the appropriate bitmap and of appropriate size
	//the hover cell's BitmapDrawable is drawn on top of the bitmap every
	//single time an invalidate call is made
	private BitmapDrawable getAndAddHoverView(View v) {
		int w = v.getWidth();
		int h = v.getHeight();
		int top = v.getTop();
		int left = v.getLeft();

		Bitmap b = getBitmapWithBorder(v);

		BitmapDrawable drawable = new BitmapDrawable(getResources(), b);

		mHoverCellOriginalBounds = new Rect(left, top, left + w, top + h);
		mHoverCellCurrentBounds = new Rect(mHoverCellOriginalBounds);

		drawable.setBounds(mHoverCellCurrentBounds);

		return drawable;
	}

	//draws a grey border over the screenshot of the view passed in
	private Bitmap getBitmapWithBorder(View v) {
		Bitmap bitmap = getBitmapFromView(v);
		Canvas can = new Canvas(bitmap);

		Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());

		Paint paint = new Paint();
		paint.setStyle(Paint.Style.STROKE);
		paint.setStrokeWidth(LINE_THICKNESS);
		paint.setColor(getResources().getColor(R.color.grey));

		can.drawBitmap(bitmap, 0, 0, null);
		can.drawRect(rect, paint);

		return bitmap;
	}

	//returns a bitmap showing a screenshot of the view passed in
	private Bitmap getBitmapFromView(View v) {
		Bitmap bitmap = Bitmap.createBitmap(v.getWidth(), v.getHeight(), Bitmap.Config.ARGB_8888);
		Canvas canvas = new Canvas (bitmap);
		v.draw(canvas);
		return bitmap;
	}

	//stores a reference to the views above and below the item currently
	//corresponding to the hover cell. It is important to note that if this
	//item is either at the top or bottom of the list, mAboveItemId or mBelowItemId
	//may be invalid.
	private void updateNeighborViewsForID(long itemID) {
		int position = getPositionForID(itemID);
		DrawerListAdapter adapter = ((DrawerListAdapter)getAdapter());
		mAboveItemId = adapter.getItemId(position - 1);
		mBelowItemId = adapter.getItemId(position + 1);
	}

	//retrieves the view in the list corresponding to itemID
	public View getViewForID (long itemID) {
		int firstVisiblePosition = getFirstVisiblePosition();
		DrawerListAdapter adapter = ((DrawerListAdapter)getAdapter());
		for(int i = 0; i < getChildCount(); i++) {
			View v = getChildAt(i);
			int position = firstVisiblePosition + i;
			long id = adapter.getItemId(position);
			if (id == itemID) {
				return v;
			}
		}
		return null;
	}

	//retrieves the position in the list corresponding to itemID
	public int getPositionForID (long itemID) {
		View v = getViewForID(itemID);
		if (v == null) {
			return -1;
		} else {
			return getPositionForView(v);
		}
	}

	//dispatchDraw gets invoked when all the child views are about to be drawn.
	//by overriding this method, the hover cell (BitmapDrawable) can be drawn
	//over the listview's items whenever the listview is redrawn
	@Override
	protected void dispatchDraw(Canvas canvas) {
		super.dispatchDraw(canvas);
		if (mHoverCell != null) {
			mHoverCell.draw(canvas);
		}
	}

	@Override
	public boolean onTouchEvent (MotionEvent event) {
		switch (event.getAction() & MotionEvent.ACTION_MASK) {
			case MotionEvent.ACTION_DOWN:
				mDownX = (int)event.getX();
				mDownY = (int)event.getY();
				mActivePointerId = event.getPointerId(0);
				break;
			case MotionEvent.ACTION_MOVE:
				if (mActivePointerId == INVALID_POINTER_ID) {
					break;
				}

				int pointerIndex = event.findPointerIndex(mActivePointerId);

				mLastEventY = (int) event.getY(pointerIndex);
				int deltaY = mLastEventY - mDownY;

				if (mCellIsMobile) {
					mHoverCellCurrentBounds.offsetTo(mHoverCellOriginalBounds.left,
							mHoverCellOriginalBounds.top + deltaY + mTotalOffset);
					mHoverCell.setBounds(mHoverCellCurrentBounds);
					invalidate();

					handleCellSwitch();

					mIsMobileScrolling = false;
					handleMobileCellScroll();

					return false;
				}
				break;
			case MotionEvent.ACTION_UP:
				touchEventsEnded();
				break;
			case MotionEvent.ACTION_CANCEL:
				touchEventsCancelled();
				break;
			case MotionEvent.ACTION_POINTER_UP:
				//if a multitouch event took place and the original touch dictating
				//the movement of the hover cell has ended, then the dragging event
				//ends and the hover cell is animated to its corresponding position
				//in the listview
				pointerIndex = (event.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >>
						MotionEvent.ACTION_POINTER_INDEX_SHIFT;
				final int pointerId = event.getPointerId(pointerIndex);
				if (pointerId == mActivePointerId) {
					touchEventsEnded();
				}
				break;
			default:
				break;
		}
		return super.onTouchEvent(event);
	}

	//this method determines whether the hover cell has been shifted far enough
	//to invoke a cell swap. If so, then the respective cell swap candidate is
	//determined and the data set is changed. Upon posting a notification of the
	//data set change, a layout is invoked to place the cells in the right place.
	//Using a ViewTreeObserver and a corresponding OnPreDrawListener, we can
	//offset the cell being swapped to where it previously was and then animate it to
	//its new position
	private void handleCellSwitch() {
		final int deltaY = mLastEventY - mDownY;
		int deltaYTotal = mHoverCellOriginalBounds.top + mTotalOffset + deltaY;

		View belowView = getViewForID(mBelowItemId);
		View mobileView = getViewForID(mMobileItemId);
		View aboveView = getViewForID(mAboveItemId);

		boolean isBelow = (belowView != null) && (deltaYTotal > belowView.getTop());
		boolean isAbove = (aboveView != null) && (deltaYTotal < aboveView.getTop());

		if (isBelow || isAbove) {

			final long switchItemID = isBelow ? mBelowItemId : mAboveItemId;
			View switchView = isBelow ? belowView : aboveView;
			final int originalItem = getPositionForView(mobileView);

			if (switchView == null) {
				updateNeighborViewsForID(mMobileItemId);
				return;
			}

			swapElements(mLists, originalItem, getPositionForView(switchView));

			((BaseAdapter) getAdapter()).notifyDataSetChanged();

			mDownY = mLastEventY;

			final int switchViewStartTop = switchView.getTop();

			mobileView.setVisibility(View.VISIBLE);
			switchView.setVisibility(View.INVISIBLE);

			updateNeighborViewsForID(mMobileItemId);

			final ViewTreeObserver observer = getViewTreeObserver();
			observer.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
				public boolean onPreDraw() {
					observer.removeOnPreDrawListener(this);

					View switchView = getViewForID(switchItemID);

					mTotalOffset += deltaY;
				
					int switchViewNewTop = switchView.getTop();
					int delta = switchViewStartTop - switchViewNewTop;

					switchView.setTranslationY(delta);

					ObjectAnimator animator = ObjectAnimator.ofFloat(switchView,
							View.TRANSLATION_Y, 0);
					animator.setDuration(MOVE_DURATION);
					animator.start();

					return true;
				}
			});
		}
	}

	private void swapElements(LinkedHashMap<Integer, ShoppingList> shoppingLists, int indexOne, int indexTwo) {
		List<Entry<Integer, ShoppingList>> rest = new ArrayList<Entry<Integer, ShoppingList>>();
		for (Entry<Integer, ShoppingList> entry : shoppingLists.entrySet()) {
			rest.add(entry);
		}
		shoppingLists.clear();
		Entry<Integer, ShoppingList> temp = rest.get(indexOne);
		rest.set(indexOne, rest.get(indexTwo));
		rest.set(indexTwo, temp);

		for (Entry<Integer, ShoppingList> entry : rest) {
			shoppingLists.put(entry.getKey(), entry.getValue());
		}
	}

	//resets all the appropriate fields to a default state while also animating
	//the hover cell back to its correct location
	private void touchEventsEnded () {
		final View mobileView = getViewForID(mMobileItemId);
		if (mCellIsMobile|| mIsWaitingForScrollFinish) {
			mCellIsMobile = false;
			mIsWaitingForScrollFinish = false;
			mIsMobileScrolling = false;
			mActivePointerId = INVALID_POINTER_ID;

			//if the autoscroller has not completed scrolling, we need to wait for it to
			//finish in order to determine the final location of where the hover cell
			//should be animated to
			if (mScrollState != OnScrollListener.SCROLL_STATE_IDLE) {
				mIsWaitingForScrollFinish = true;
				return;
			}

			mHoverCellCurrentBounds.offsetTo(mHoverCellOriginalBounds.left, mobileView.getTop());

			ObjectAnimator hoverViewAnimator = ObjectAnimator.ofObject(mHoverCell, "bounds",
					sBoundEvaluator, mHoverCellCurrentBounds);
			hoverViewAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
				@Override
				public void onAnimationUpdate(ValueAnimator valueAnimator) {
					invalidate();
				}
			});
			hoverViewAnimator.addListener(new AnimatorListenerAdapter() {
				@Override
				public void onAnimationStart(Animator animation) {
					setEnabled(false);
				}

				@Override
				public void onAnimationEnd(Animator animation) {
					mAboveItemId = INVALID_ID;
					mMobileItemId = INVALID_ID;
					mBelowItemId = INVALID_ID;
					mobileView.setVisibility(VISIBLE);
					mHoverCell = null;
					setEnabled(true);
					invalidate();
				}
			});
			hoverViewAnimator.start();
		} else {
			touchEventsCancelled();
		}
		mDrawerLayout.requestDisallowInterceptTouchEvent(false);
	}

	//resets all the appropriate fields to a default state
	private void touchEventsCancelled () {
		View mobileView = getViewForID(mMobileItemId);
		if (mCellIsMobile) {
			mAboveItemId = INVALID_ID;
			mMobileItemId = INVALID_ID;
			mBelowItemId = INVALID_ID;
			mobileView.setVisibility(VISIBLE);
			mHoverCell = null;
			invalidate();
		}
		mCellIsMobile = false;
		mIsMobileScrolling = false;
		mActivePointerId = INVALID_POINTER_ID;

		mDrawerLayout.requestDisallowInterceptTouchEvent(false);
	}

	//this TypeEvaluator is used to animate the BitmapDrawable back to its
	//final location when the user lifts his finger by modifying the
	//BitmapDrawable's bounds
	private final static TypeEvaluator<Rect> sBoundEvaluator = new TypeEvaluator<Rect>() {
		public Rect evaluate(float fraction, Rect startValue, Rect endValue) {
			return new Rect(interpolate(startValue.left, endValue.left, fraction),
					interpolate(startValue.top, endValue.top, fraction),
					interpolate(startValue.right, endValue.right, fraction),
					interpolate(startValue.bottom, endValue.bottom, fraction));
		}

		public int interpolate(int start, int end, float fraction) {
			return (int)(start + fraction * (end - start));
		}
	};

	//determines whether this listview is in a scrolling state invoked
	//by the fact that the hover cell is out of the bounds of the listview;
	private void handleMobileCellScroll() {
		mIsMobileScrolling = handleMobileCellScroll(mHoverCellCurrentBounds);
	}

	//this method is in charge of determining if the hover cell is above
	//or below the bounds of the listview. If so, the listview does an appropriate
	//upward or downward smooth scroll so as to reveal new items.
	public boolean handleMobileCellScroll(Rect r) {
		int offset = computeVerticalScrollOffset();
		int height = getHeight();
		int extent = computeVerticalScrollExtent();
		int range = computeVerticalScrollRange();
		int hoverViewTop = r.top;
		int hoverHeight = r.height();

		if (hoverViewTop <= 0 && offset > 0) {
			smoothScrollBy(-mSmoothScrollAmountAtEdge, 0);
			return true;
		}

		if (hoverViewTop + hoverHeight >= height && (offset + extent) < range) {
			smoothScrollBy(mSmoothScrollAmountAtEdge, 0);
			return true;
		}

		return false;
	}

	public void setShoppingLists(LinkedHashMap<Integer, ShoppingList>  mLists) {
		this.mLists = mLists;
	}

	//this scroll listener is added to the listview in order to handle cell swapping
	//when the cell is either at the top or bottom edge of the listview. If the hover
	//cell is at either edge of the listview, the listview will begin scrolling. As
	//scrolling takes place, the listview continuously checks if new cells became visible
	//and determines whether they are potential candidates for a cell swap.
	private AbsListView.OnScrollListener mScrollListener = new AbsListView.OnScrollListener () {

		private int mPreviousFirstVisibleItem = -1;
		private int mPreviousVisibleItemCount = -1;
		private int mCurrentFirstVisibleItem;
		private int mCurrentVisibleItemCount;
		private int mCurrentScrollState;

		public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount,int totalItemCount) {
			mCurrentFirstVisibleItem = firstVisibleItem;
			mCurrentVisibleItemCount = visibleItemCount;

			mPreviousFirstVisibleItem = (mPreviousFirstVisibleItem == -1) ? mCurrentFirstVisibleItem
					: mPreviousFirstVisibleItem;
			mPreviousVisibleItemCount = (mPreviousVisibleItemCount == -1) ? mCurrentVisibleItemCount
					: mPreviousVisibleItemCount;

			checkAndHandleFirstVisibleCellChange();
			checkAndHandleLastVisibleCellChange();

			mPreviousFirstVisibleItem = mCurrentFirstVisibleItem;
			mPreviousVisibleItemCount = mCurrentVisibleItemCount;
		}

		@Override
		public void onScrollStateChanged(AbsListView view, int scrollState) {
			mCurrentScrollState = scrollState;
			mScrollState = scrollState;
			isScrollCompleted();
		}

		//this method is in charge of invoking 1 of 2 actions. Firstly, if the listview
		//is in a state of scrolling invoked by the hover cell being outside the bounds
		//of the listview, then this scrolling event is continued. Secondly, if the hover
		//cell has already been released, this invokes the animation for the hover cell
		//to return to its correct position after the listview has entered an idle scroll
		//state.
		private void isScrollCompleted() {
			if (mCurrentVisibleItemCount > 0 && mCurrentScrollState == SCROLL_STATE_IDLE) {
				if (mCellIsMobile && mIsMobileScrolling) {
					handleMobileCellScroll();
				} else if (mIsWaitingForScrollFinish) {
					touchEventsEnded();
				}
			}
		}

		//determines if the listview scrolled up enough to reveal a new cell at the
		//top of the list. If so, then the appropriate parameters are updated.
		public void checkAndHandleFirstVisibleCellChange() {
			if (mCurrentFirstVisibleItem != mPreviousFirstVisibleItem) {
				if (mCellIsMobile && mMobileItemId != INVALID_ID) {
					updateNeighborViewsForID(mMobileItemId);
					handleCellSwitch();
				}
			}
		}

		//determines if the listview scrolled down enough to reveal a new cell at the
		//bottom of the list. If so, then the appropriate parameters are updated
		public void checkAndHandleLastVisibleCellChange() {
			int currentLastVisibleItem = mCurrentFirstVisibleItem + mCurrentVisibleItemCount;
			int previousLastVisibleItem = mPreviousFirstVisibleItem + mPreviousVisibleItemCount;
			if (currentLastVisibleItem != previousLastVisibleItem) {
				if (mCellIsMobile && mMobileItemId != INVALID_ID) {
					updateNeighborViewsForID(mMobileItemId);
					handleCellSwitch();
				}
			}
		}
	};

	public void setDrawerLayout(DrawerLayout mDrawerLayout) {
		this.mDrawerLayout = mDrawerLayout;
	}
}
